This invention relates generally to turbomachinery, and specifically to stator vanes for the compressor or fan section of a gas turbine engine. In particular, the invention concerns a compressor or fan assembly with vibration damped stator vane airfoils.
Gas turbine engines provide reliable, efficient power for a wide range of applications, including aviation and industrial power generation. In modern applications, the gas turbine is typically built around a power core made up of a compressor, combustor and turbine section, arranged in flow series with an upstream inlet and downstream exhaust.
The compressor section compresses air from the inlet, which is mixed with fuel in the combustor and ignited to generate hot combustion gas. The turbine section extracts energy from the expanding combustion gas, and drives the compressor via a common shaft. Energy is delivered in the form of rotational energy in the shaft, reactive thrust from the exhaust, or both.
Small-scale gas turbine engines generally utilize a one-spool design, with co-rotating compressor and turbine sections. Larger-scale combustion turbines, jet engines and industrial gas turbines (IGTs) are typically arranged into a number of coaxially nested spools, which operate at different pressures and temperatures, and rotate at different speeds.
The individual compressor and turbine sections in each spool are subdivided into a number of stages, which are formed of alternating rows of rotor blade and stator vane airfoils. The airfoils are shaped to turn, accelerate and compress the working fluid flow, and to generate lift for conversion to rotational energy in the turbine.
Aviation applications include turbojet, turbofan, turboprop and turboshaft configurations. Turbojets are an older design, in which thrust is generated primarily from the exhaust. Modern fixed-wing aircraft typically employ turbofan and turboprop engines, in which the low pressure spool is coupled to a propulsion fan or propeller. Turboshaft engines are used on rotary-wing aircraft, including helicopters.
In turbofan engines, the fan rotor typically operates as a first stage compressor, or as the pre-compressor stage for a low-pressure compressor or booster module. Fan and compressor airfoils are thus subject to similar design considerations, and the term compressor blade may encompass both the fan and compressor sections.
Both compressor and fan airfoils are also subject to operational effects, including natural mode excitations, for example, in the low pressure stages, where airfoil dimensions and vibration amplitudes can be large. These vibrations impose a range of corresponding engineering constraints, including the need for strong, durable and impact-resistant airfoil designs, in lightweight, cost-effective configurations with increased service life and reliability. With respect to vibration response, however, rotor and stator stages may have substantially different characteristics, particularly for unshrouded (fixed-free) rotor blades, as opposed to shrouded (fixed-fixed) stator vanes.